Baker et al., U.S. Pat. No. 3,669,939 disclose highly branched condensation polymers prepared from polyhydroxymonocarboxylic acids (OH).sub.n R--CO.sub.2 H wherein R is a hydrocarbon radical of up to 22 carbon atoms optionally interrupted by a heteroatom, and n is 2-6. Monomers disclosed as particularly suitable are those of the formula (HOCH.sub.2).sub.2 --C(R.sup.3)CO.sub.2 H wherein R.sup.3 is alkyl or --CH.sub.2 OH. Aromatic monomers are not exemplified.
P. J. Flory, J. Amer. Chem. Soc., 74, 2718 (1952), "Principles of Polymer Chemistry", Cornell University Press, 1953, pp. 361-370, discusses the theory of condensation polymerization of so-called AB.sub.n -type monomers wherein A and B functions condense together to form branched high polymers which attain high molecular weight without gelation. The theory predicts that polymerization of such monomers containing one A and B.sub.n functions leads to randomly branched polymers containing one unreacted A function and (n-1)x+1 unreacted B functions where x is the number of monomer units, said polymers being more polydisperse the higher the degree of polymerization. Examples of monomers of this type given by Flory are benzyl halides XCH.sub.2 --C.sub.6 H.sub.5, alkali metal salts of trihalophenols and D-glucose; the polymers are said to be soluble, non-crystalline and fusible when correctly prepared. Fully aromatic monomers of the AB.sub.n -type, or polymers therefrom, are not disclosed.
Maciejewski, J., Macromol. Sci.-Chem., A17 (4), 689 (1982) describes his concept of so-called shell topological compounds, preparation of which includes polymerization of a monomer of the XRY.sub.n -type, wherein n is at least 2. Such polymerization results in a "cascade branched (uncrosslinked) molecule of spherical structure". Equations are provided which correlate, among other properties, molecular weight with sphere diameter. Although monomers employed in the present invention are of the XRY.sub.n -type, the reference does not suggest polymerization of arylene monomers or the physical properties of the polyarylenes therefrom.
Tomalia et al., U.S. Pat. No. 4,587,329; 4,568,737; 4,588,120; 4,507,466 and WO 84/02705 disclose dense star polymers containing core, core branches and terminal groups. These polymers are built up, layer after layer, from a core substance by selective condensation of functional groups; each successive layer becomes a core for the subsequent layer. Only aliphatic polyamides and polyethers are exemplified. The monomers are of the AB.sub.n -type and the polymers therefrom are said to be soluble and to have a molecular volume less than 80% of that of a conventional extended star polymer made from similar materials, molecular diameters being less than 2000 angstrom units.
U.K. Patent Application GB 2,132,626 discloses a method for producing aromatic polyesters by polycondensation of A: aromatic hydroxycarboxylic acids, or A with B: one or more compounds selected from aromatic dicarboxylic acids and C: one or more compounds selected from aromatic diphenols, and on said polycondensation, adding D: one or more compounds selected from the group consisting of aromatic trihydroxy compounds, aromatic dihydroxy-monocarboxylic acids and aromatic monohydroxydicarboxylic acids.
Kricheldorf et al., Polymer [11], 23, 1821 (1982) disclose the preparation of branched poly (3-hydroxybenzoate) by condensation of 3-(trimethylsiloxy)benzoyl chloride and 3,5-(bistrimethylsiloxy)benzoyl chloride, said polycondensate remaining uncrosslinked regardless of degree of conversion.
The prior art does not disclose soluble, highly branched polyesters prepared by self-polycondensation of AB.sub.n -type monomers wherein n is at least 2 and wherein B moieties contain a terminal carboxylic acid group or derivative thereof, or wherein either A or B is a carboxyl or hydroxyl-terminated moiety which is an aromatic or aliphatic amino. By soluble is meant that the polyester is soluble to at least 5% in solvents such as tetrahydrofuran, dimethylacetamide, acetone, chloroform or hexafluoroisopropanol.